1. Field of the Invention
The present invention relates to an automatic gear transmission and more particularly to an apparatus for setting selection gate positions for change speed in a gear-shift mechanism of the automatic gear transmission.
2. Discussion of the Prior Art
In a conventional gear-shift mechanism of an automatic gear transmission including a changeover shaft mounted within a housing of the gear transmission for both axial and rotary movements to be axially shifted from a neutral position to a forward or reverse position in a select direction and to be rotated at its shifted position in shifting operation, a shift-and-select lever fixed to an intermediate portion of the changeover shaft for axial and rotary movements therewith, an interlock member rotatably mounted in place on the changeover shaft and having a pair of interlock arms located at the opposite sides of the shift-and-select lever, detent means for restricting rotary movement of the interlock member and for permitting axial movement of the interlock member, a plurality of fork shafts mounted in parallel within the housing for axial movement in a shift direction perpendicular to the select direction, a plurality of shift forks mounted on the fork shafts to be selectively engaged with each sleeve of a plurality of changeover mechanisms for selectively establishing a plurality of change-speed gear trains in the gear transmission, a plurality of shift heads mounted on the fork shafts to be selectively engaged with the shift-and-select lever at their neutral positions, the shift-and-select lever is selectively engaged with one of the shift heads at a selection gate position and moved to a low or high speed side during which the other shift heads are retained in their neutral positions by engagement with the interlock arms. If the selection gate position was deviated from a proper position for engagement with the selected shift head, the shift-and-select lever would be brought into frictional contact with the other shift head adjacent thereto during movement to the low or high speed side or would not be moved due to contact with the other shift head.
It is, therefore, a primary object of the present invention to provide an apparatus for accurately setting selection gate positions for change speed in the gear-shift mechanism without causing any problems described above.
According to the present invention, the object is accomplished by providing an apparatus for setting selection gate positions for change speed in a gear-shift mechanism of an automatic gear transmission including a changeover shaft mounted within a housing of the gear transmission for both axial and rotary movements to be axially shifted from a neutral position to a forward or reverse position in a select direction and to be rotated at its shifted position in shifting operation, a shift-and-select lever fixed to an intermediate portion of the changeover shaft for axial and rotary movements therewith, an interlock member rotatably mounted in place on the changeover shaft and having a pair of interlock arms located at the opposite sides of the shift-and-select lever, detent means for restricting rotary movement of the interlock member and for permitting axial movement of the interlock member, a plurality of fork shafts mounted in parallel within the housing for axial movement in a shift direction perpendicular to the select direction, a plurality of shift forks mounted on the fork shafts to be selectively engaged with each sleeve of a plurality of changeover mechanisms for selectively establishing a plurality of change-speed gear trains in the gear transmission, a plurality of shift heads mounted on the fork shafts to be selectively engaged with the shift-and-select lever at their neutral positions, a first actuator operatively connected to the changeover shaft for effecting rotary movement of the changeover shaft when activated under control of an electronic controller, a shift-stroke sensor for detecting operation of the first actuator, a second actuator operatively connected to the changeover shaft for effecting axial movement of the changeover shaft in the select direction when activated under control of the electronic controller, and a selection-stroke sensor for detecting operation of the second actuator, wherein the electronic controller comprises a program memory storing instructions for activating the first actuator such that the shift-and-select lever is rotated to shift one of the shift heads engaged therewith in its neutral position to a low or high speed side in the shift direction, for activating the second actuator to effect movement of the shift-and-select lever with the changeover shaft in the select direction in a condition where the shift head was shifted to the low or high speed side, for deactivating the second actuator when the movement of the shift-and-select lever in the select direction was restricted by engagement with the shift head shifted to the low or high speed side, for reading out an output value of the selection-stroke sensor when the second actuator was deactivated, and for setting a selection gate position of the shift head shifted to the low or high speed side on a basis of the output value of the selection-stroke sensor.